Dr. Aristotle G. Koutsiaris

General Department of Larissa, Geopolis, University of Thessaly, Greece

^*Corresponding author:Dr. Aristotle G. Koutsiaris, General Department of Larissa, Geopolis, University of Thessaly, Trikalon Ring Road, 41110 Larissa, Greece

Abstract

Keywords: Wall Shear Stress, Microfluidics, Organs on chip, Humans, Eye, Microcirculation, Arterioles, Venules

Wall Shear Stress (WSS) is a very important biomechanical stimulus in the function of the circulatory system, the Blood-Brain Barrier (BBB) [1] and the endothelial autophagy [2]. In order to study the effect of WSS scientists make in vitro models and microfluidic organs on chip [1, 3]. A key aspect of these in vitro models is simulating WSS with values of physiological level [3].

Therefore, I would like to call attention to the papers of Koutsiaris et al [4, 5] where WSS was quantified in vivo from noninvasive measurements of blood flow velocity in the human eye precapillary arterioles, capillaries and postcapillary venules. Even though WSS levels between 3 and 20 dynes/cm2 used to be considered as “physiological”, it is now known that WSS can easily reach greater values. More specifically, 3 points are now clear: 1) a significant arteriolar velocity pulsation, attenuates slowly (logarithmically) as blood proceeds down to smaller arteriolar diameters in the human eye [6], 2) the velocity pulse corresponds to a WSS pulse which can reach values of 200 dynes/cm2 at the precapillary arteriolar side and 3) average arteriolar WSS values are more than double than those in the venular side for the same diameters [1].

Finally, taking into account the sophisticated role of endothelial cells in the cardiovascular system, acting as cardiovascular processing sensors (CPSs) [1], and the principle of segmental heterogeneity [7], the microfluidic model designers should consider simulating five different microvascular segments, as recently proposed [1]: arteriolar, precapillary arteriolar, capillary, postcapillary venular and venular. Hopefully, the above information will be helpful to the authors and readers of your journal.

References

1. Koutsiaris AG. Wall shear stress in the human eye microcirculation in vivo, segmental heterogeneity and performance of in vitro cerebrovascular models. Clin Hemorheol Microcirc. 2016; 63(1): 15-33.

2. Yao P, Zhao H, Mo W, et al. Laminar shear stress promotes vascular endothelial cell autophagy through upregulation with Rab4. DNA Cell Biol. 2016; 35(3): 118-123.

3. Van der Helm MW, Van der Meer AD, Eijkel JCT, et al. Microfluidic organ-on-chip technology for blood-brain barrier research. Tissue Barriers. 2016; 4: 1e1142493.

4. Koutsiaris AG, Tachmitzi SV, Batis N, et al. Volume flow and wall shear stress quantification in the human conjunctival capillaries and post-capillary venules in-vivo. Biorheol. 2007; 44(5/6): 375-386.

5. Koutsiaris AG, Tachmitzi SV, Batis N. Wall shear stress quantification in the human conjunctival pre-capillary arterioles in-vivo. Microvasc Res. 2013; 85: 34-39.

6. Koutsiaris AG. The resistive index as a function of vessel diameter in the human carotid arterial tree. Microvasc Res. 2013; 89: 169-171.

7. Boegehold MA. Heterogeneity of endothelial function within the circulation. Current Opinion in Nephrology and Hypertension. 1998. 7: 71-78.

Received: April 18, 2019;
Accepted: May 13, 2019;
Published: May 16, 2019.

To cite this article : Aristotle G. Koutsiaris. Human Microvessel Wall Shear Stress. Japan Journal of Medicine. 2019: 2:3.

© Koutsiaris AG, et al. 2019.